Radio receiving apparatus



July 28, 1931. B. B. MINNIUM I RADIO RECEIVING APPARATUS Filed Nov. 25,1927 Q; 4 A H25 v O I Q Q: Q g R m f- A m Q C\ Qf U H 1 TOD/13.MUULl/LL/TL Patented July 28 1931 f fumreo A COREGRAFION 6i DELL ir-LAKEM V d g I I g v v more nEcEIvING'nrrABA rUs I hiiplfcatidnfil'edNovember 25,1927. east Ni 23 5,5 2 1.

-This invention relates to radiore'ceiv ing sets of thekin'd in which,for one reason or another, there'is ordina'fiily some liability of aburn or ripple voltageiti the amplifier out- "Generall stated, the'object of the invention is to provide improved construct-ion and'eireuit rrangement whereby the said hum or'ripple veitage is prevented,or at least it) greatly redueemevenwhen alternating cur, rent isemployed for heating or energizing the filament of the am lifier, thusimproving the receiving qualities of a receiving set of thiskind. v l vIt is elso'anebiiect' to provide certain details' a'rid features of imrovement and com binatieiis tending'to increase the general efficiencyand the desirabilityef-aradio receiving set of this particularClltlftICl'ilK id To these and other useful ends, the invention consistsin the matters hereinafter set forth and claimed, and shown in theaccompan'y'iiig drawings, in which the single diagraiiiiliustratesaradio receiving set involv- 456 the principles cf the invention.

, As thus illustrated, the invention comrises: an ordi ary aerial 1',which is connected to ground 2 through the primary ot an ordinaryinduction or repeating coil. The secondary 4 of said induction coil andthe adjustable condenser 5 are connected in,

parallel or in shunt of each other, at the points v by a conductor 8 tothe grid 9 of the first vacuum tube or amplifier, while the junctionpoint 7 isconnected by the conductors 10 and Y 11 to the ground 2, asshown. The conductor 10 is also connected through the conductor 12 withthe negative pole of the battery 13, While the positive pole of thisbattery is connected by the conductor 1 L with the intermediate point 15on the resistance 16, as shown. The filament 17 of said tube oramplifier has its terminals connected to the opposite ends of thesecondary 18 of the transformer or induction coil 19, and a resistance20 is connected in bridge across the filamentcircuit, as shown. Theconductor 12 islconnected through aresistance 21 with the ustable point22 on the resistance 20,

' c'nnected to the filament. I

tlft-e tube or amplifier is connected a can:

6 and 7, and the point 6 is connected (anode Y potential wherebynegative pole-o 'i the battery i3 is I The plate 23 of (motor 24 withthe junction petites, where v by said plate connected to one terminal of26, and with oneteriniiial at the res'istaiice I the inim-ye? of thsecond induction or repeating coil, The lowe terminals resistance 96 andrimary winding] 27 are connected together by a conductor 28, as shown;The resistances 16 a r'1d'i26 are "con:- nected togetherin any suitablemanner, for example, bya slide having" movable contacts 2 9' and 30 forengaging said resistances, re spec-tively. The input circuit of thesecond stage of amplification includes secondary 31,as'shown; I V V V IIt will also he seen that th diagram, which is illustrative of oneiorinof the invention,

includes a primary32 for the transformer 19, to which is connected aplug???" that can be inscrtedin any electrical base or receptacle whichhas connection with a source of alt er In this way, the

nating current sup-plyf tra sformer coils rs and 32 are adapted to ofthe g co=o'pe'r'ate to su ply alternating current to, v

the filament 17 of the first stageei amplifiertion; willbe seen thatanother secondary' 34 is also included in the transformer 19, sothat thefilaments of second stage of amplification is also heated ot energizedby'a-lternatingcurrent.

In e-i'dii ar rec" iv'n sets of this kiiiLtlie control of gain (orvolume) is usually by varying the filament (cathode) or plate In the use"of tubes or amplifiers i'n which the filament or electron -'emittingelement is heatedbyaIternating cur- -i"-eiit, normaro ei-atirig valuesof plate and filament voltage must be maintained in order tepi-ev'eiithufn or rip le vdltager'iiithe ain'- plifiei, output. The eireii i'tshown and described,jttiiichis illustrati; f *irieformbf the"iii-ve'n't'bn, sei vesstohpidth e plate voltage v I rent) constant, butvitriestheaiiiqunt sip-late (and therefore the plate energy flowingthrough the tran former or 1 iridtictieii'ceil' primar 2"? te which' itis con-- nected. If rim ry- 27 ig retttiv ly in met,-

is may be omitted.

WVhen the resistance of the primary coil 27 is high, the fixed point 15must be placed near the lower end of the resistance 16, and theresistance of this coil 16 must be so proportioned as to always maintaina fixed value of resistance between this fixed point 15 and the plate 23of the tube or amplifier.

It is obvious that the invention may be employed in connection with anyoutput primary alone, or in connection with two or more outputprimaries, as may be desired. But Whether the invention is employed inone form or another, the adjustment of the con tact points 29 and 30 (orthe contact 30 alone if the resistance 16 is not necessary) can beemployed to eliminate any hum or ripple voltage in the amplifier output,while at the same time varying the volume. In other words, the object ofthe invention is to provide means for easily and satisfactorily varyingor changing the volume without producing objectionable hum or ripplevoltage.

It will be seen that the zero point on resistance 16 is reached when themovable points 29 and 30 are moved downward until point 29 is oppositepoint 15 on the resistance. Thus, while one resistance is increasing,the other resistance is decreasing, so to speak, by adjustment of thepoints 29 and 30 in either direction, in any range of adjustment abovethe fixed point 15, connected with the source of plate potential. Inother words, each reslstance varies reversely to the other, for as oneincreases, the other diminishes, and vice versa, according to thedirection in which the points 29 and 30 are adjusted. The point 15 canbe attached wherever necessary on the 'coil 17, depending upon theresistance of the primary 27 of the transformer.

Without disclaiming anything, and without prejudice to any noveltydisclosed, what I claim as my invention is:

1. In a radio receiving set, an amplifier output induction coil primaryhaving a re sistance in shunt thereof, and having the source of platepotential connected to a variable point between the ends of saidresistance, including a variable resistance be tween said source andsaid first mentioned re sistance.

2. In a radio receiving set, an amplifier output induction coil primaryhaving a resistance in shunt thereof, and having the source of platepotential connected to a va riable point between the ends of saidresistance, including a variable resistance between said source and saidfirst mentioned resistance, there being a variable point for engagingsaid variable resistance between the ends thereof, and said variablepoints being adjustable in unison.

3. In a radio receiving set, an amplifier output induction coil primaryhaving a resistance in shunt thereof, and having the source ofplatepotential connected to a variable point between the ends of saidresistance, including a variable resistance between said source and saidfirst mentioned resistance, there being a variable point for engagingsaid variable resistance between the ends thereof, and said variablepoints being adjustable in unison, said variable points and saidresistances being so relatively arranged that as more of one resistanceis included in the plate circuit, less of the other resistance isincluded therein, and vice versa, by the adjustment of said points inunison in one direction, or in the opposite direction.

4. In a radio receiving set, an amplifier output induction coil primaryhaving a resistance in shunt thereof, and having the source of platepotential connected to a Variable point between the ends of saidresistance, including a variable resistance between said source and saidfirst mentioned resistance,with means whereby one resistance variesreversely to the other.

5. In a radio receiving set, an amplifier output induction coil primaryhaving a variable resistance in shunt thereof, so that the coil and moreor less of said resistance are in multiple in the plate circuit, and avariable resistance in series with said resistance in the plate circuit.

6. A structure as specified in claim 5, having means whereby eachresistance is necessarily variable in unison with the other, butreversely thereto.

7. A structure as specified in claim 5, said source being connected toan intermediate point on said last mentioned resistance.

8. A structure as specified in claim 5 having means whereby any portionof said resistance which at any time is not in shunt of said Jrimary isin series therewith in the plate circuit.

Specification signed this 22nd day of November, 1927.

BYRON B. MINNIUM.

